181. The most commonly used method for the refining of impure metals is electrolysis.
Answer: Refining
182. After being left in the air for some time, _______ turns black.
Answer: Copper
183. A homogeneous mixture of two or more metals or a metal and a non-metal is called ________.
Answer: Alloy
184. The electrical conductivity and melting point of an alloy is _______ compared to that of a pure metal.
Answer: Lower
185. Non-metals do not _______ displace hydrogen from dilute acids.
Answer: Hydrogen
186. Plaster of Paris is a white powder, and when mixed with water, it turns into ________.
Answer: Gypsum
187. In the chlor-alkali process, _______ gas is given off at the anode.
Answer: Chlorine
188. Aqua regia is a fresh mixture made in the ratio of concentrated hydrochloric acid and concentrated nitric acid of ________.
Answer: 3:1
189. _______ does not react with dilute HCl.
Answer: Copper
190. Ores mined from the earth are generally contaminated with a large quantity of impurities such as soil, sand, etc., which are called ________.
Answer: Gangue
191. Acid + Metal → Salt + _______
Answer: Hydrogen gas
192. Alkalis generate _______ ions in water.
Answer: OH-
193. The pH value decreases.
Answer: Hydronium
194. Present in vinegar.
Answer: Acetic acid
195. When baking soda is heated or mixed with water, _______ is produced, which raises bread or cake and makes them fluffy and soft.
Answer: Carbon dioxide
196. Sulfide ores convert to oxides when heated strongly in the presence of excess air. This process is called _______.
Answer: Roasting
197. An alloy of lead and tin is called.
Answer: Solder
198. Alkaline potassium permanganate or acidified potassium dichromate oxidizes alcohol to _______.
Answer: Aldehyde
199. Alcohol reacts with sodium to produce _______.
Answer: Hydrogen
200. _______ causes blindness by affecting the optic nerve.
Answer: Methanol